1. Field of the Invention
The present invention relates to a timepiece such as a portable timepiece like a wristwatch or a pocket watch, a table clock, and a wall-hanging timepiece.
2. Description of Related Art
Regarding a wristwatch, etc., various constructions are known in which an edge member supporting a transparent member (usually made of glass) opposite a dial is mounted to a case band of a case.
In a first example, an insertion portion including a part of the edge member and having a circular outer periphery is inserted from the front side of the case into an interior which is formed in the case band and the inner periphery of which is surrounded by a circular edge member mounting portion, and, between the insertion portion and the edge member mounting portion, there is held a ring formed of soft plastic in a state in which it is compressed in the radial direction of the case. Due to this construction, the edge member is mounted to the case band via the ring. In this mounting condition, the edge portion of the edge member supporting the transparent member covers the edge member mounting portion while in contact with the edge member mounting portion from the front side of the case.
In a second example, an insertion portion including a part of the edge member and having a circular outer periphery is forced from the front side of the case into an interior which is formed in the case band and the inner periphery of which is surrounded by a circular edge member mounting portion, and an engagement groove formed so as to be open in the inner peripheral surface of the edge member mounting portion and an engagement protrusion protruding from an outer peripheral surface of the insertion portion of the edge member are engage with each other in a hooked fashion. Due to this construction, the edge member is mounted to the case band in a state in which the edge member mounting portion is held between the edge portion of the edge member supporting the transparent member and the engagement protrusion. In this mounting state, the edge portion of the edge member covers the edge member mounting portion while in contact with the edge member mounting portion from the front side of the case.
In a third example, an inner peripheral surface of an edge member mounting portion which is formed on a case band and the inner periphery of which is circular, and an outer peripheral surface of an insertion portion which includes a part of an edge member, the outer periphery of which is circular, and which is surrounded by the edge member mounting portion of the case band, are respectively formed as inclined surfaces gradually reduced in diameter as they extend toward the front side of a case. And, the insertion portion is forced into the interior surrounded by the edge member mounting portion. As a result, the edge member is mounted to the case band in a state in which the inner peripheral surface of the edge member mounting portion and the outer peripheral surface of the insertion portion are in contact with each other. In this mounting state, the edge portion of the edge member supporting a transparent member covers the edge member mounting portion while in contact with the edge member mounting portion from the front side of the case.
When performing correction during the production of a timepiece, and when performing maintenance on the timepiece, the edge member may be detached from the case band. In this case, in the above first through third examples, a tool is inserted between the edge member mounting portion and the edge portion of the edge member covering the same, and prying is performed with this tool, whereby the edge member is detached. Thus, as the edge member is pried open, the case band and the edge member may be damaged.
Further, in the first through third examples, when the edge member is mounted to the case band through the operation of inserting or forcing the insertion portion of the edge member into the interior surrounded by the edge member mounting portion of the case band, and also when the edge member is detached from the case band as described above, it is impossible to avoid stress from acting on the edge portion. Thus, in the construction in which the transparent member is supported by the edge portion of the edge member by using adhesive, there is a fear of adhesive separation due to the above-mentioned stress. To cope with this, it is necessary to adopt a construction in which soft plastic is provided between the edge portion of the edge member and the transparent member, so that the degree of freedom in terms of design for supporting the transparent member is rather low.
In addition, in the above-mentioned third example, when the edge member is repeatedly attached and detached to and from the case band, both the inner peripheral surface of the edge member mounting portion and the outer peripheral surface of the insertion portion of the edge member interfere with each other, and the possibility of scraping is high. Thus, the reproducibility for appropriately mounting the edge member to the case band is low.
On the other hand, there is known a wristwatch free from the various problems mentioned above (e.g., See JP-A-2002-189084 (Patent Document 1)).
In this wristwatch, in the edge member supporting the transparent member, there is formed a screw hole reaching the edge portion, and, in the case band accommodating a movement with hands and a dial, there is formed a screw escape hole communicating with the screw hole of the edge member. And, a screw inserted into the screw escape hole from the rear surface (back surface) of the case band toward the screw hole is screwed into the screw hole of the edge portion, with a waterproof gasket being arranged between the edge portion of the edge member and the edge member mounting portion of the case band covered with this edge portion. Through the fastening of this screw, the edge member is drawn toward the rear surface side from the front surface side of the case, and the edge member is mounted to the case band, with the edge portion of the edge member covering the edge member mounting portion while in contact with the edge member mounting portion from the front side of the case.
The insertion portion that the edge member supporting the transparent member has determines the display diameter of the dial arranged inside the case band opposite the transparent member. Here, the display diameter of the dial is the diameter of the dial region except for the peripheral portion of the dial supported by and covered with this edge member; in other words, it is the diameter of the dial region visible through the transparent member, and is smaller than the outer diameter of the dial.
The display diameter is prescribed as described above, whereby, when the width of the edge member, above all, the width of the edge portion is large, the display diameter of the dial is small in the case where the size of the case is prescribed; further, in the case where the display diameter of the dial is prescribed, the size of the case is large.
With the advance of the recent aging society, there is a demand for an increase in the display diameter of the dial. In this case, the size of the human wrist is as it was in the old days, so that, in the case of a wristwatch, for example, there is a demand for an increase in the display diameter of the dial while suppressing an increase in the size of the case.
In the wristwatch disclosed in Patent Document 1, however, the screw for fixing the edge member to the case band is arranged on the outer side of the outer periphery of the dial, and the screw hole is provided at the edge portion of the edge member in conformity with the screw escape hole through which this screw is passed. The wristwatch disclosed in Patent Document 1, in which the edge portion thus has a screw hole, the width of the edge member thereof is large. Thus, the wristwatch disclosed in Patent Document 1 cannot meet the demand mentioned above.